Abstract Media are a normative part of life for most children and adults with most individuals spending several hours each day using various media devices. However, as many as 10% of individuals develop an addictive or pathological use of media, which impairs their ability to function in daily life. Existing research on pathological media use has focused on adolescents and emerging adults; however trajectories of both pathological and healthy relationships with media likely begin well before adolescence. It is necessary to study the trajectories of media use, and in particular problematic and healthy media use, earlier in child development. This will allow researchers to discover the root of the problem before a true pathological use of media has developed. The long-term goal is to understand media-related problematic behavior in early childhood and its contribution to the development of pathological media use later in life. Problematic media use in early childhood involves a host of likely precursors to later pathological media use, including a fixation on media, tantrums or crying when media is removed, and sneaking or lying about media. The objective of this particular application involves two specific aims (1) to determine incidence and predictors of problematic and healthy media use during a 3-year longitudinal study in early childhood (from ages 4 to 6) and (2) to examine the risk and protective factors of problematic and healthy media use, with a focus on media content (i.e. violent, prosocial, and educational), media context (i.e. parenting behaviors around media) and child characteristics (i.e. child physiological reactivity and impulsivity). The central hypothesis is that around 10% of children will develop problematic media use during early childhood, with such use being relatively stable over time after it first occurs. Additionally, we hypothesize that we will be able to predict distinct media trajectories by examining media content, context, and child characteristics. We will leverage our existing sample of 269 children and their parents whom we have been studying since shortly after birth in order to examine a media trajectory from birth to 6 years of age. We will do this by using a number of innovative methods including passive sensing apps that track time spent using media, observational methods, and experience sampling methodology to capture problematic media use in the moment. The proposed research is significant, because this project will be the first longitudinal study in the digital age to discover the risk and protective factors related to the trajectory of problematic media use across the early childhood period. This knowledge will help researchers identify high-risk individuals that might benefit from early intervention aimed at changing the trajectory of media exposure, to balance media with other activities and to increase healthy media use. This may dramatically reduce the number of individuals who develop a pathological relationship with media later in development.